Method for removal of lithography from containers

ABSTRACT

The applied finish or lithography of cylindrical containers such as aerosol type containers is removed by passing the container through a zone of intense heat and then immediately into a second zone where the cylindrical surface of the container is brushed while hot and while the lithography is soft. A plurality of containers are preferably urged seriatim along a linear path through an induction heating coil and are then engaged by one or more wire brushes which rotate the container during the brushing operation. The process may be carried out rapidly and automatically without damage to the soldered seam or metallurgy of the container.

United States Patent [191 7 Gregory et al.

[1 1 3,801,369 Apr. 2, 1974 METHOD FOR REMOVAL OF LITHOGRAPHY FROMCONTAINERS Inventors: Joseph J. Gregory, 1929 Stratford,

Westchester, 111. 60153; Jack R. Randolph, Box 148, Bismarck, 111. 61814Filed: Oct. 31, 1972 Appl. No.: 302,495

U.S. Cl 134/6, 15/21 D, 15/70, 15/88, 101/425, 134/19, 134/33, 134/38Int. Cl B08b l/02, B08b 7/04 Field of Search 134/6, 19, 38, 5, 33; 15/21D, 70, 88, 104.04; 101/425 References Cited UNITED STATES PATENTS 5/1949Perrault et al. 15/104.04

8/1942 Bailey 134/19 X 2/1940 Vincent-Daviss 134/6 12/1960 Winkler..134/19 3,641,608 2/1972 Kratt 15/88 Primary Examiner-S. Leon BashoreAssistant ExaminerRichard H. Tushin Attorney, Agent, or Firm-Gary,Juettner, Pigott &

Cullinan [57] ABSTRACT may be carried out rapidly and automaticallywithout.

damage to the soldered seam or metallurgy of the container.

10 Claims, 7 Drawing Figures MTENTEIJAPR 2 I974 3801; 389

- sum 1 or 3 I 1 METHOD FOR REMOVAL OF LITI-IOGRAPI'IY FROM CONTAINERSBACKGROUND OF THE INVENTION Aerosol containers have gained wideacceptance for the storing and dispensing of a wide variety of products.Such containers are made of steel sheet to withstand considerablepressure and are usually cylindrical in shape, having a soldered axialseam along one side, and soldered seams joining the cylindrical wall tothe top and bottom. The walls are plated or coated with tin to preventrusting of the steel. The product under pressure within the container isdispensed by a valve arrangement usually located at the top of thecontainer.

Aerosol and similar containers are normally provided with lithography inthe form of a coating of paint, enamel, varnish or other suitablefinish, which protects the metal surface from deterioration and containsprinted information'to identify the product. In most cases, lithographycomprising the product name, description, instructions for use and otherinformation or design is printed on the container surface in accordancewith specifications provided by a particular customer, and thelithography is then covered by a clear varnish.

After the lithography has been applied, the container acquires aspecific identity that is useful only to the customer for whom it wasmade, even though the container alone might be useful in otherapplications. Large scale production and misapplication of lithographyoften results in an excessive number of a given lot of containers thatcannot be sold. Due to the high cost of containers of this type, itwould be desirable to devise a method for completely removing thelithography to allow use of the container for another purpose.

In order to change the identity of the container, it is possible toapply a printed label or paper cover over the cylindrical surface, whichhides the old lithography and allows use of the container for adifferent product. This procedure may be dangerous, however, because thelabel or cover is normally applied with minimal amounts of adhesive andis susceptible to removal. For example, if a container with hair sprayor deodorant lithography was converted by application of a label to apaint spray container, and the label was later inadvertently removed,the container would become a dangerous instrument, viz., an unsuspectingconsumer would use paint as hair spray or deodorant.

The use of solvents for the removal of lithography is not feasiblebecause the varnishes used to overcoat the printing resins are of thesilicone or epon type and resist most standard solvents. There are otherdrawbacks in the use of solvents, such as possible contamination of theinterior of the container, disposal of waste solvent and lithographyresidue, health and safety hazards in the use of volatile solvents, andhigh solvent costs.

SUMMARY OF THE INVENTION The present invention provides a method andapparatus for completely and inexpensively removing lithography from thecylindrical surface of a container, whereby the container may be used inanother application without the possibility of confusion. Thelithography is removed by first softening the lithography by rapid anduniform heating of the cylindrical surface,

followed by brushing of the surface. The containers may then be used forany desired purpose by applying an appropriate label. The process allowsfor complete removal of the lithography without damage to the solderedseams or to the tin plating on the container.

The apparatus generally comprises a means for carrying or conveying thecontainers on their side through a heating zone, preferably through thecoils of an induction heater, and means for passing each containerbetween a rotating brush and a bearing support, whereby the containersare brushed while being rotated.

THE DRAWINGS FIG. 1 is a simplified elevational view of the apparatus ofthe present invention, illustrating the various process steps of theinvention;

FIG. 2 is a sectional view taken substantially along section line 2-2 ofFIG. 1;

FIG. 2a is a sectional view taken substantially along section line 2a-2aof FIG. 1;

FIG. 3 is a simplified elevational view of another embodiment of thepresent invention;

FIG. 4 is a sectional view through the apparatus of FIG. 3 taken alongsection line 4-4 thereof;

FIG. 5 is a simplified perspective view of a further embodiment of thepresent invention; and

FIG. 6 is a sectional view taken along section line 66 of FIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The preferred embodiment of theinvention is shown in FIGS. 1 and 2, which illustrate an apparatus forremoving lithography from the cylindrical surface 10 of an aerosolcontainer 12 having the usual top dome 14 and valved outlet 16. It willbe appreciated, however, that the apparatus shown is capable of removingcured or hardened paint, enamel, varnish, and any other similar coatingfrom a cylindrical object of any length.

The device generally comprises conveyor means for moving the cylindricalobjects on their sides along a line, heating means for heating thesurface of the object to soften the lithography thereon, and abrasionmeans engageable with the heated surface of the object to remove thesoftened lighography therefrom.

The conveyor means, generally indicated at 18, preferably comprises apair of spaced parallel shafts 20 and 22, one of which is driven, witheach shaft, respectively, having a pair of axially spaced pulleys 24 and26 secured thereon. Respective pulleys 24 are aligned with the otherpulleys 26 to mount a pair of spaced parallel belt loops 28 and 30,which are stretched between their respective pulleys to define asubstantially horizontal upper moving bed upon which the containers maybe conveyed in a straight line on their cylindrical surface in adirection indicated by arrows in FIG. 1. The belts 28 and 30, which arecomposed of reinforced rubber or the like, are spaced apart a distancewhich is less than the diameter of the container 12, such that thecontainer is nested between the upper flights of the belts 28 and 30, asshown in FIG. 2.

The heating means is preferably in the form of a spiral induction coil32 having a sufficiently large enough diameter to closely accommodatefree passage of the belts 28 and 30 and the conveyed container 12therethrough. The induction coil is conventional and comprises hollowcopper tubing through which cool water is circulated, with the tubingbeing connected to a source of high frequency direct or alternatingcurrent. As the container passes through the coil on the belts, it isheated by means of eddy currents induced by the high frequency fieldsurrounding the coil. The coil is of sufficient length and size to causerapid and uniform heating of the entire container in a very short periodof time, since the time residence of the container within the inductioncoil must be a fraction of a second to allow fast and efficienttreatment of a large number of containers. In the embodiment shown inFIG. 1, the coil 32 is preferably energized continuously while thecontainers are successively moved therethrough.

The temperature to which the container is heated is important and mustbe controlled by the length of the induction coil, the number of turnsin the coil, the spacing between adjacent coil turns, as well as thespeed of the conveyor. Generally, the maximum temperature reached by thecontainer must be high enough to soften the surface coating but must beless than the melting point of the solder in the side joint commonlyfound in containers of this nature. Too high a temperature will causeleaks or structural failure in the container and may burn the containeror melt the tin coating on the steel. Generally speaking, theseconditions are attained if the containers are heated to a temperature offrom about 340F to 390F, although temperatures of up to 45()I arepossible with some types of containers.

The means for abrading the containers comprises a separate conveyormeans cooperating with the first conveyor and one or more drivencylindrical brushes engageable with the cylindrical surface of thecontainer.

As shown in FIGS. 1 and 2a, a sprocket 34 having a radius less than thepulleys 26 is rotatably mounted between said spaced pulleys on the exitend of the conveyor 18, and a driven second sprocket 36 is mounted on ashaft 38 spaced from and parallel to the shaft 24. The roller chain 40having outwardly projecting spaced dogs or lugs 42 is wrapped around thesprockets and is driven thereby. In addition, a pair of spaced parallelfixed rods 44 extend substantially in the same plane as the upper flightof the conveyor 18 from the exit end thereof with the chain 40 locatedtherebetween. The rods 44 are spaced apart for a distance less than thediameter of the containers 12 so as to support the containers during thebrushing operation.

As the containers exit from the belt conveyor 18, they are transferredto the rods 44 and are then engaged by a lug 42 of the chain 40, saidlug being of sufficient length to extend above the level of the rods andengage a shoulder of the can between the dome l4 and the cylindricalsurface 10. The lugs 42 serve to push the container along the rods 44and into engagement with successive ones of a plurality of rotatingbrushes 46, which may be mounted on a common shaft 48.

The brushes 46 are preferably wire brushes, comprising a plurality ofspaced disks to provide a series that is longer than the length of thecontainer. Narrower brushes are preferred because they tend to conformbetter to the actual shape of the container and better accommodate dentswhich may be present in the surface of the container. Although highquality wire brushes having 0.006 inch diameter bristles are preferred,one sizes and materials, such as nylon, may be successfully employed.The shaft 48 is preferably adjustably spaced a sufficient distancedirectly above the chain 40 such that a moving container will be engagedbetween the rods 44 and successive brushes 46. The axis of the shaft 48is in the vertical plane of the container axes to hold the containers onthe rods 44 without slippage to either side. As the containers are movedinto engagement with the brushes 46, the rotary motion of the brushescauses the containers to be rotated somewhat about their axes, therebyexposing the entire cylindrical surface of the container to brushing.

Although the containers may be conveyed through the apparatus in acontiguous relationship, it has been found preferable to convey thecontainers through the coil 32 in a slightly spaced relationship, i.e.,at least about a one inch spacing, which increases the efficiency anduniformity of the heating process. When conveyed in a contiguousrelationship, it has been found that the ends of the container are notsufficiently heated by the induction coil, and traces of lithography arenot removed at the ends.

Means, as shown in the left hand portion of FIG. 1, are provided forplacing containers onto the belt conveyor in a timed, spacedrelationship. A pusher, comprising a power cylinder 50 is mounted on asupport 52 and includes an extendable and retractable rod 54 having anenlarged head 56 engageable with the crown 14 or valve 16 of a container12. A pair of spaced parallel rods 58 are mounted on the support 52 withthe rod 54 and head 56 operating in parallel therebetween, said rodsextending parallel to and in register with the top flight of theconveyor 18. The rods 58 serve to support successive containers whichare pushed off the rods and onto the conveyor 18 in a predeterminedsequence.

The cylinder 50 is preferably activated at regular intervals by asuitable valve (not shown) to push successive containers 12 onto theconveyor 18. A loading mechanism 60 comprises an inclined ramp or asequence feed mechanism is connected to the support 52 in front of therod head 56 and serves to load successive of a plurality of containers12a onto the spaced rods 58.

In operation, it may be seen that each container travels insubstantially a straight line from the pusher to the heater and then tothe brusher, and the containers travel in a spaced relationship withtheir domes l4 facing away from the direction of travel to assure properengagement with the lugs 42. The coil 32 is continuously energized, andas each container is passed through the coil, it is quickly heated,whereby the lithography on the cylindrical surface becomes soft. Theheated container is then passed into the brushes 46, which physicallyremoves the lithography as the container is being pushed and rotated onthe rods 44. The containers may then be led away from the apparatus andmay also be inverted and cleaned free of dust by a jet of pressurizedair. Thereafter, the containers are rendered suitable for use by theapplication of a label on the cylindrical surface.

The version of the invention shown in FIGS. 3 and 4 allows thecontainers 60 to be cleaned in a contiguous fashion. A pair of spacedsupport members 62 and 64 extend through an induction coil 66 andbeneath a brush assembly 68. A power cylinder 70 equipped with a rod 72having a pusher 74 is engageable with the bottom surface of successivecontainers introduced on The coil 66 is arranged in a particular mannerto assure that the contiguous containers are uniformly heated. For thispurpose, the containers 50 are jogged on the supports 62 by the cylinder70 into successive forward positions. The coil 66 has more closelyspaced and additional turns in the zones corresponding to the ends ofthe containers than in the middle, such that additional heat isgenerated at the ends. The coil is long enough to accommodate at leasttwo and preferably at least three containers at any given time, suchthat the containers are progressively heated by successive portions ofthe coils as they are indexed forward at fixed intervals and distances,with one container pushing the next successive container through theapparatus.

In the version shown in FIGS. 3 and 4, the coil is not energizedcontinuously but is pulsed in sequence with the container movement, oreach time a container is advanced into a new position. In this manner,the containers gradually reach the desired temperature for lithographyremoval and are heated evenly, notwithstanding their contiguousrelationship.

The embodiment shown in FIGS. 5 and 6 illustrate a different form ofheating. The containers 80 are slidably conveyed on spaced parallel rods82 and 84 from one end of the apparatus to the other by means of a chaindrive 86 including spaced lugs 88 projecting from the chain and engagingand pushing the ends of the conveyors.

The initial portion of the rods 82 and 84 and chain drive 86 aresurrounded or at least partially enclosed by a oven wall 90 having aplurality of electrical resistance heating elements 92 mounted therein,said elements being spaced from but substantially parallel to the rods82 and 84. The energization of the elements 92 serves to heat theinterior of the chamber, thereby heating the containers as they passtherethrough.

As in the previous embodiments, the far end of the conveying line isequipped with suitable brushes 94 which are driven by a motor 96. In theembodiment shown, the rods 82 and 84 are rotatable about their axes. Asthe brushes 94 engage the containers 80, the rods 82 and 84 are rotated,thereby rotating the supported containers in the heating chamber toprovide more uniform heating.

We claim:

1. A method for removing lithography from the cylindrical outer surfacesof containers in the absence of solvent contact comprising the steps ofconveying the containers on their cylindrical surfaces along a path, andwhile being conveyed, heating the containers to a temperature sufficientto soften the coveringof lithography upon the cylindrical surfacesthereof, and then brushing the cylindrical surfaces of the thus heatedcontainers to effect lithography removal therefrom.

2. The method of claim 1 wherein the containers are heated by conveyingthem through an energized electrical induction coil.

3. The method of claim 2 wherein the containers are passed in a spacedrelationship through a continuously energized induction coil.

4. The method of claim 2 wherein the containers are jogged through aninduction coil and the coil is momentarily energized in sequence witheach jog.

5. The method of claim 4 wherein the containers are jogged in acontiguous end to end relationship and the coil is arranged to effectmore heating at the ends of the container than in the middle.

6. The method of claim 1 wherein the containers are heated by passagethrough a heated oven.

7. The method of claim 1 wherein the step of brush-- ing comprisessupporting the container on one portion of its cylindrical surface, andengaging another portion of the cylindrical surface with a rotatingbrush with sufficient force to cause the container to rotate about itsaxis.

8. The method of claim 1 wherein the containers are heated to atemperature of from about 340 to about 450F.

9. A method of removing lithography from the cylindrical outer surfaceof an aerosol can in the absence of solvent contact comprising the stepsof first heating the cylindrical surface to a temperature sufficient tosubstantially soften the lithography thereon, and then brushing saidcylindrical surface to remove said lithography.

10. A method of removing lithography from the cylindrical outer surfaceof a container in the absence of solvent contact comprising the steps ofsupporting the container with its axis substantially horizontal, heatingthe container to a temperature of from about 340 to about 450F, and thenimmediately brushing the heated cylindrical surface along an upwardlyfacing area thereof by a brush rotating on an axis substantiallyparallel to said substantially horizontal axis while the containerrotates on a horozontal axis.

2. The method of claim 1 wherein the containers are heated by conveyingthem through an energized electrical induction coil.
 3. The method ofclaim 2 wherein the containers are passed in a spaced relationshipthrough a continuously energized induction coil.
 4. The method of claim2 wherein the containers are jogged through an induction coil and thecoil is momentarily energized in sequence with each jog.
 5. The methodof claim 4 wherein the containers are jogged in a contiguous end to endrelationship and the coil is arranged to effect more heating at the endsof the container than in the middle.
 6. The method of claim 1 whereinthe containers are heated by passage through a heated oven.
 7. Themethod of claim 1 wherein the step of brushing comprises supporting thecontainer on one portion of its cylindrical surface, and engaginganother portion of the cylindrical surface with a rotating brush withsufficient force to cause the container to rotate about its axis.
 8. Themethod of claim 1 wherein the containers are heated to a temperature offrom about 340* to about 450*F.
 9. A method of removing lithography fromthe cylindrical outer surface of an aerosol can in the absence ofsolvent contact comprising the steps of first heating the cylindricalsurface to a temperature sufficient to substantially soften thelithography thereon, and then brushing said cylindrical surface toremove said lithography.
 10. A method of removing lithography from thecylindrical outer surface of a container in the absence of solventcontact comprising the steps of supporting the container with its axissubstantially horizontal, heating the container to a temperature of fromabout 340* to about 450*F, and then immediately brushing the heatedcylindrical surface along an upwardly facing area thereof by a brushrotating on an axis substantially parallel to said substantiallyhorizontal axis while the container rotates on a horozontal axis.